1. Field of the Invention
This invention relates to magnetic recording, dual stripe, magnetoresistive (DSMR) read heads and more particularly to methods of forming such read heads.
2. Description of Related Art
Askar, Magnetic Disk Drive Technology: Heads, Media, Channel, Interfaces And Integration, IEEE Press Inc., (1996) pp. 142-146, describes DSMR sensors and exchange biasing.
U.S. Pat. No. 5,262,914 of Chen et al. for "Magnetoresistive Head with Enhanced Exchange Bias Field" describes a MnFe AntiFerro-Magnetic (AFM) bias layer in direct contact with a NiFe MR layer which in turn is in physical contact with an interdiffusion layer composed of a noble metal, with a 240.degree. C., 7 hour annealing process for thermally forming an interface between the AFM layer and the MR layer which produces an exchange bias field to the MR layer.
U.S. Pat. No. 5,406,433 of Smith for "Dual Magnetoresistive Head for Reproducing Very Narrow Track Width Short Wavelength Data" describes at Col. 5, line 54 to Col. 6, line 33 longitudinal biasing of MR elements in opposite directions by pinning at the ends of the elements by use of patterned exchange biasing. After an MR element is deposited a patterned exchange layer of FeMn is deposited over the two ends of the first MR element. Either during (1) deposition of the AFM FeMn exchange layer or (2) after annealing, a longitudinal magnetic field is applied to the structure to orient the exchange bias field in the selected longitudinal direction. After formation of a spacer and the second MR element, a second patterned ferrimagnetic (TbCo) exchange layer of a different material from the AFM FeMn layer is deposited over the two ends of the second MR element. A post deposition field in the opposite direction from the first field is applied to the TbCo layer so that there is opposite magnetization in the two MR elements.
U.S. Pat. No. 5,561,896 of Voegeli et al. for "Method of Fabricating Magnetoresistive Transducer" teaches a Selective Pulse Interdiffusion (SPI) process during which areas destined to become biasing segments of an MagnetoResistive (MR) head are selectively heated using one or more electrical current pulses of short duration.
U.S. Pat. No. 5,684,658 of Shi et al. for "High Track Density Dual Stripe Magnetoresistive (DMSR) Head" shows a DSMR having a first anti-ferromagnetic (AFM) longitudinal biasing layer and a second anti-ferromagnetic (AFM) longitudinal biasing layer that are parallel, in contrast with the present invention as described at Col. 8, lines 20-39. The AFM materials include NiMn, CoCr, CoCrPt, CoCrTa, CoCrNi, CoCrPtNi, CoCrNiTa, etc.
U.S. Pat. No. 5,696,654 of Gill et al. for "Dual Element Magnetoresistive Sensor with Anti-Parallel Magnetization Directions for Magnetic State Stability" describes a dual MR element sensor with two MR elements separated by a high resistivity, conductive spacer element. A layer of a hard bias material abutting the track edges of the MR2 element biases it longitudinally in one direction. The MR1 layer is biased by a pair of exchange bias layers (NiFe/NiMn or NiFe/NiO) abutting the track edges of the MR1 strip by exchange coupling in an opposite, i.e. antiparallel longitudinal direction.
U.S. Pat. No. 5,859,753 of Ohtsuka et al. for "Spin Valve Magnetoresistive Head with Spun Valves Connected in Series" that includes first and second magnetization pinning layers which are anti-parallel to each other including AFM layers one of which is NiMn that has a high blocking temperature and one of which if FeMn that has a low blocking temperature. At col. 10, lines 10-19 ". . . NiMn having a high blocking temperature is formed as the first antiferromagnetic layer . . . on the first magnetization pinning layer . . . at a temperature of 200.degree. to 300.degree. C. The NiMn is grown in a magnetic field H.sub.o1 applied in the first direction. Thereafter, . . . FeMn is formed as the second antiferromagnetic layer . . . on the second magnetization spinning layer . . . at a temperature of around 160.degree. C. While applying a magnetic field H.sub.o2 in the direction opposite to the first direction, the growth of FeMn is carried out." At Col. 10, lines 37-60 it is pointed out that an alternative process can employ a step of heating to the higher blocking temperature and application of field H.sub.o1 which is followed by a step of heating to the lesser blocking temperature temperature and application of field H.sub.o2 can be deferred until after formation of the AFM layers.